The Study of Inner Surface Crack Formation of Seamless Modified 9Cr-1Mo Tube Rolled on Mandrel Mill and Its Application

Abstract:

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The hot workability of modified 9Cr-1Mo, as a grade of heat resistant steels, is inferior to that of low-alloy steel, so the inner surface crack (ISC) easily occurs in seamless boiler tubes produced by the Mandrel Mill under improper rolling conditions. With the aid of FEM, the metal flow status during the rolling process was analyzed in 140mm 8-stand mandrel mill of Bao Steel. Both the metallographic shape and size of the ISC together with the result from the simulation show that the ISC of seamless tube forms at the elongation stage of shell. The mechanism of the ISC was discussed. With its initiation in stand No.1 and No.2 due to poor hot workability of modified 9Cr-1Mo steel, the ISC develops in subsequent passes. Based upon the mechanism devised was a special roll pass system which substantially upgraded the yield of qualified products.

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Periodical:

Materials Science Forum (Volumes 561-565)

Main Theme:

Edited by:

Young Won Chang, Nack J. Kim and Chong Soo Lee

Pages:

61-64

Citation:

S. Z. Li et al., "The Study of Inner Surface Crack Formation of Seamless Modified 9Cr-1Mo Tube Rolled on Mandrel Mill and Its Application", Materials Science Forum, Vols. 561-565, pp. 61-64, 2007

Online since:

October 2007

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$38.00

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[3] J. Xu: Academic thesis for M.D. Anhui University of Technology (2007) (in Chinese).

[4] S.Z. Li, Y.D. Yin, J. Xu, J.G. Xue, J.M. Zheng and F. Pan: Analysis of stress/strain features and ductile fracture tendency of thick-walled structural steel tube during continuous rolling process with mandrel mill, in: The 3rd International Conference on Advanced Structural Steels (Aug. 21-24, Gyeongju, Korea, 2006), p.439.

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